Communication systems link together two communication devices so that the devices can send information to each other in a call or other communication event. Information may include voice, text, images or video.
One such communication system is a peer to peer system, in which a plurality of end users can be connected for communication purposes via a communications structure such as the internet. The communications structure is substantially decentralised with regard to communication route switching therein for connecting the end users. That is, the end users can establish their own communication routes through the structure based on exchange of one or more authorisation certificates (user identity certificates—UIC) to acquire access to the structure. The structure includes an administration arrangement issuing the certificates to the end users. Such a communication system is described in WO 2005/009019.
Peer-to-peer systems and other communication systems that use the internet or any other packet switched network employ voice over IP (internet protocol) protocols (VoIP) to transmit data. These systems are commonly referred to as VoIP systems. VoIP systems are beneficial to the user as they are often of significantly lower cost than communication networks, such as fixed line or mobile networks, otherwise referred to as public switched telephone networks (PSTN). This may particularly be the case for long distance calls.
The connection of two communication devices using more than one type of network is becoming increasingly common. In some cases a call may be transmitted via more than one network in an attempt to reduce the cost of the call. For example a call between two devices located in a PSTN network may be transmitted via the internet. In other cases it is necessary to transmit the call via two networks when each device is located in a different network.
Gateways are provided at the interface between different networks to translate call data from a form required by a protocol of one network into a form required by a protocol of another network. However in some cases some data associated with the call may not be supported by the protocol of one of networks. In this case the data associated with the call is lost.
For example a communication device such as a mobile phone located in a PSTN network may be arranged to identify the origin of an incoming call. However if the call has originated from a device located in the internet the PSTN network cannot recognise and transmit the identity of user of the device to the mobile phone. As such the identity of the calling party will be lost.